1. Field of the Invention
This invention relates to apparatus for guiding a moving web uniformly with respect to a fixed center line.
2. Description of the Prior Art
Many devices have been devised for edge guiding and centering a moving web with respect to a fixed center line. Some of the prior art devices, like the present invention, include co-acting rolls which are angularly inclined in the direction of travel of the web for engaging opposite faces of a marginal region of the web and in various ways exert lateral forces on the web tending to position the web relative to a fixed center line. However, many of the prior art devices which included co-acting rolls depend upon a mechanical finger, air jet, photo cell, or other sensor to detect the presence, or absence of the edge of the web and to signal an air cylinder, electric solenoid, or the like to vary the pressure at the nip of the rolls and thus to effect the guiding action of angularly disposal rolls. Such devices because they require a sensor and associated mechanism to vary the roll pressure are of varying degrees of complexity.